Breadcrumb Home > Dictionary > Index M mercy killing: Meaning and Definition of Find definitions for: mer'cy kill"ing Pronunciation: [key] euthanasia (def. 1). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. mercy mercy seat ✖ Related Content Daily Word Quiz: hortatory Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language